Monoalkylcatechol derivatives are used as intermediates for pharmaceuticals and agricultural chemicals. The method of preparing them by alkyl-etherification of only a hydroxy group on one side of a corresponding catechol derivative and the method of preparing them by hydroxylation of a corresponding alkoxybenzene derivative have been mainly known. As to the former, the alkyl-ether method by dialkyl sulfate (Japanese Patent Publication (A) No. 112485/1993), and the alkyl-ether method by an alcohol and an acid catalyst (Japanese Patent Publication (A) No. 305546/1992) are illustrated. As to the latter, the method by reaction with hydrogen peroxide under formic acid (Bull. Chem. Soc. Jpn., 1989, 62, 1652-1657), the method by reaction with Fe (IV)-EDTA ascorbic acids (J. Mol. Catal. 1982, 14, 333-340), the method by reaction with peracetic acid (Nippon Kagaku Kaishi 1979, 370-374), and the method of synthesis by photo oxidization under Lewis acid (Chem. Lett., 1972, 179-180) are illustrated.
However, the above known methods are generally inferior in a yield and a position-selectivity. Accordingly, the mixture of regioisomers forms and it is difficult to separate each other so that these methods are not suitable for preparing the intermediates of pharmaceuticals and agricultural chemicals which require high purity. Expensive reagents and raw materials which are difficult to obtain, are sometimes used and therefore, these known methods are not satisfied in the industrial production.
The present inventors engaged extensively in solving the above problems, and have found a new process for preparation of a catechol derivative almost without any by-products and in a high yield and that in a high purity almost without contamination of regioisomers.